I. Field of Invention
This invention relates to a diagnostic test for gastrointestinal disorders in humans to determine whether a meal being digested in the stomach is emptied into the small intestine at a normal rate. In pathologic states, the rate can be abnormally accelerated or diminished.
II. Background of Invention
During gastric emptying, ingested food is mixed with gastric juices. After appropriate dilution, the food is then emptied into the small bowel for further digestion and absorption. This is a complex, carefully regulated system involving hormones, receptors, nerves, and muscles of the stomach, and a consistent rate and concentration of the final content is emptied into the small bowel. Many factors, such as the fat composition or type of protein in the food, affect this carefully regulated emptying of liquids.
The emptying mechanism can be affected by many disorders and lead to either delayed emptying or rapid emptying (dumping). Delayed emptying can lead to symptoms of nausea, vomiting, abdominal pain, and poor growth. Dumping can lead to retching, abdominal pain, flatulence, diarrhea, poor weight gain, and dangerously low blood glucose levels. To establish a diagnosis and enable further medical management of a patient, the rate of gastric emptying often must be measured. There are various therapies for delayed or rapid emptying, but their efficacy is often unclear. The rates for emptying for solids and liquids differ. In infants and small children, the rate of liquid emptying is particularly important.
Current methods of measuring gastric emptying, called nuclear gastric emptying scans, use radioactive materials added to the milk or formula and require the patient to lie still for several hours for the scanning. Expensive nuclear imaging suites, available commonly only in major centers and with radiation safety-related requisites, are needed. In addition, the scans are not possible in those individuals who cannot lie still or are too sick to be transported to an imaging center. The patient is required to be supine, must remain still for at least an hour, and is not able to participate in normal activities. The impact of these unnatural requirements remains unclear. With radioactive scanning, test results vary according to the direction of the scan (from the front or back), and there is lack of standardization. These tests are unsuitable for infants and children because of potential risks of radiation and the need to be immobilized. Finally, because these tests use a radioactive tracer, normal values in adults as well as in children and pregnant women, are not available, making interpretations of mild abnormalities difficult.
Other methods, although not currently routinely used, using non-radioactive materials (e.g., octanoic acid and acetate with heavy carbon, 13C) have been shown to correlate with nuclear scanning. However, in every case studied so far, the tracer used must first be absorbed by the cells lining the small bowel, called enterocytes, be transported to the liver, and then be metabolized before the heavy carbon is detectable as carbon dioxide in the breath. This results in a delay in measuring the rate of gastric emptying using breath samples. Also, these materials are not currently available for clinical use for liquid gastric emptying, and their usefulness has been found to be limited to comparisons of samples within one individual. They also require complex calculations to account for the delay between their absorption and the appearance of carbon dioxide in breath.
Accordingly, there is a need for a new and improved test that is non-invasive, safe, and accurate and which can be performed with minimal inconvenience and discomfort to a patient.
The first objective of the present invention is to provide a new and improved test to measure gastric emptying that is non-invasive, safe, and accurate. The second objective is to provide a test to measure gastric emptying that can be performed in the office setting. The third objective of the present invention is to provide a test to measure gastric emptying that can be performed during normal activities without requiring the patient to lie still or be restrained. Lastly, the fourth objective is to provide a test to measure gastric emptying that can be repeated frequently without risk.
These objectives are attained in the present invention which provides a new method for measuring gastric emptying in which 13C-glutamine or 13C-glutamic acid is administered orally to a patient and breath samples are taken from the patient at periodic intervals and analyzed for carbon dioxide. More particularly, at least one breath sample is taken prior to the administration of the 13C-glutamine or 13C-glutamic acid and at least one sample is taken subsequent to the administration of the 13C-tracer (e.g., the 13C-glutamine or 13C-glutamic acid) and the method for analyzing for carbon dioxide can distinguish between 12C-carbon dioxide and 13C-carbon dioxide and at least measure the relative amounts of 12C-carbon dioxide and 13C-carbon dioxide.